Selective Precipitation (selective + precipitation)

Distribution by Scientific Domains

Selected Abstracts

Towards Understanding of the Selective Precipitation of Alkali Metal Cations in Presence of Dipicrylamine Anion

Suresh Eringathodi
Abstract Dipicrylamine anion (DPA,) precipitates out [K(DPA)] with high selectivity from salt bitterns containing Na+, K+, and Mg2+, whereas the same ligand shows poor selectivity towards K+ , and much higher selectivity towards Cs+ , in studies conducted with a mixture of K+, Rb+, and Cs+. Their single-crystal structures reveal that the K+ and Rb+ salts have similar layered structures, with 8 oxygen atoms from seven DPA, anions encapsulating the metal cation, whereas the Cs+ salt possesses a channel-like structure with the metal ion encapsulated by ten oxygen atoms from six DPA,. The conformation of DPA, in the [Cs(DPA)] single crystal matches closely that of DPA in crystalline state. M···O and intermolecular C,H···O interactions together stabilize the structures. The 133Cs NMR spectrum of the poorly soluble [Cs(DPA)] shows an upfield shift of the peak with respect to CsCl as a result of the interaction with the oxygen atoms of DPA,, whereas 23Na NMR spectrum of the highly soluble [Na(DPA)] shows no such upfield shift compared to NaCl. Powder XRD patterns of bulk [M(DPA)] (M = K+, Rb+, and Cs+) precipitates show that these are similar to the patterns obtained by simulation of the single-crystal X-ray data. The selectivity of precipitation correlates qualitatively with the size and hydration enthalpies of the ions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

DNA Depletion by Precipitation in the Purification of Cell Culture-Derived Influenza Vaccines

T. Kröber
Abstract A pilot study for the purification of cell culture-derived human influenza virus is presented, which focuses on the early removal of DNA by precipitation. Strains of influenza virus were propagated using Madin Darby canine kidney cells as a host. A harvesting time of about 72 h postinfection was chosen to minimize the level of impurities (host cell DNA and protein). Cell culture supernatant was clarified by centrifugation and the performance of this operation was characterized on the basis of Sigma theory. An average clarification efficiency of 93,% (based on turbidity) and a product yield of 85,% (based on hemagglutination activity) were obtained at a load of 1.6,·,10,8 m s,1. Furthermore, the applicability of Sigma theory for scale-up studies using two different laboratory centrifuges was verified. Selective precipitation of DNA was achieved by the addition of polyethyleneimine (PEI). Full factorial design was applied to optimize selectivity considering pH, ionic strength, and the concentration and molecular weight of PEI. Under optimized conditions, treatment with PEI resulted in a reduction of DNA to 15,% of the initial amount, while 86,% of virions (based on neuraminidase activity) were recovered. The subsequent concentration of virions was realized by tangential-flow ultrafiltration. Recovery based on hemagglutination activity was determined to 63,% on average. Including the previous precipitation step, overall reduction in DNA after tangential-flow ultrafiltration was 500-fold. These results indicate that the suggested unit operations are suited for the early depletion of DNA in cell culture-derived influenza vaccine production. [source]

LC-MSMS identification of Arabidopsis thaliana heat-stable seed proteins: Enriching for LEA-type proteins by acid treatment

E. Oliveira
Abstract Protein identification in systems containing very highly abundant proteins is not always efficient and usually requires previous enrichment or fractionation steps in order to uncover minor proteins. In plant seeds, identification of late embryogenesis abundant (LEA) proteins is often masked by the presence of the large family of storage proteins. LEA-proteins are predicted to play a role in plant stress tolerance. They are highly hydrophilic proteins, generally heat-stable, and correlate with dehydration in seeds or vegetative tissues. In the present work, we analyze the protein composition of heat-stable Arabidopsis thaliana seed extracts after treatment with trichloroacetic acid (TCA). The composition of the proteins that precipitate and those that remain in solution in 3% TCA was analyzed by two different approaches: 1D SDS-PAGE coupled to LC-ESI-MSMS analysis and a gel-free protocol associated with LC-MALDI-MSMS. Our results indicate that treating total heat-soluble extracts with 3% TCA is an effective procedure to remove storage proteins by selective precipitation and this fractionation step provides a soluble fraction highly enriched in Lea-type proteins. The analysis and determination of protein identities in this acid-soluble fraction by MS technology is a suitable system for large-scale identification of Lea-proteins present in seeds. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Optimization of RT,PCR for the Detection of Bean leaf roll virus in Plant Hosts and Insect Vectors

V. Ortiz
Abstract The detection of luteoviruses by reverse transcription polymerase chain reaction (RT,PCR) depends on the adequate quality and quantity of extracted viral nucleic acids. We have optimized the detection of Bean leaf roll virus (BLRV) using selective precipitation by LiCl of viral RNA from a small quantity of infected plant tissues and insect vectors. The optimal template for PCR was 15 ,l of RT reaction mixture. BLRV was detected in different plant hosts and aphid vectors and Aphis fabae, previously considered to be a non-vector of BLRV, was found to acquire the virus from infected plants. [source]

Toward a better analysis of secreted proteins: the example of the myeloid cells secretome

Mireille Chevallet
Abstract The analysis of secreted proteins represents a challenge for current proteomics techniques. Proteins are usually secreted at low concentrations in the culture media, which makes their recovery difficult. In addition, culture media are rich in salts and other compounds interfering with most proteomics techniques, which makes selective precipitation of proteins almost mandatory for a correct subsequent proteomics analysis. Last but not least, the non-secreted proteins liberated in the culture medium upon lysis of a few dead cells heavily contaminate the so-called secreted proteins preparations. Several techniques have been used in the past for concentration of proteins secreted in culture media. These techniques present several drawbacks, such as coprecipitation of salts or poor yields at low protein concentrations. Improved techniques based on carrier-assisted TCA precipitation are described and discussed in this report. These techniques have been used to analyze the secretome of myeloid cells (macrophages, dendritic cells) and enabled to analyze proteins secreted at concentrations close to 1,ng/mL, thereby allowing the detection of some of the cytokines (TNF, IL-12) secreted by the myeloid cells upon activation by bacterial products. [source]

Global fractionation of oak heartwood extractable polymers (lignins, polysaccharides and ellagitannins) by selective precipitations

Marie-Françoise Nonier
Abstract This paper introduces a new fractionation method by selective extractions and precipitations making it possible to collect the three groups of oak heartwood extractable polymers in a single operation. The three families, lignins, polysaccharides and ellagitannins, were obtained and each was characterized by different techniques. We grouped together the techniques used to characterize these different oak wood groups of polymers: IR, GC, GC-MS, LC-MS, 1H NMR, SEC, MALDI-TOF/MS. This work focuses on the qualitative aspect only. Copyright © 2004 Society of Chemical Industry [source]